Course indicator system for radio ranges



Feb. '24, 194s.

D. G. C. LUCK DIRECTIONAL GYRO l ATTORNEYl Patented Feb. 24, 1948 COURSE INDICATQR SYSTEM FOR RADIO RANGES David G. C. Luck, Princeton, N. J., assgnor to Radio Corporation of America, a corporation of Delaware Application December 22, 1945, Serial No. 636,970

This invention relates to improvements in radio aids to the navigation of aircraft, and more particularly to course indicator systems for use with omnidirectional radio ranges.

In general, the omnidirectional range radiates two signals: one which varies in some characteristic, such as phase, in accordance with the bearing from the range, and another which does not Vary, but'serves as a, reference for comparison with the rs't. The range signals are received on the aircraft, where they are compared With each other to provide ,direct indication of the bearing of the craft from the range station. A typical omnidirectional range system is described in U. S. Patent No. 2,253,958.

For ight along a radial line through the range station, it is desirable to have an indicator of the familiar left-might type to show any deviation of the craft from the desired course. Such indicator systems have been devised for use with `omnidirectional ranges. A typical one is described bearing selector which is manually adjustable to correspond to the bearing of the course to be followed. -As long as the aircraft is flying along the selected course, the left-right indicator reads zero, or on course. This is true whether the craft isflying toward or away from the range station.

`Likewise, the left-right indicator will read zero in most systems when the ightjis on course Whether the course bearing selector is set for the desired course, or for the reciprocal of the desired course bearing. With one setting, deviation of the craft to the right of the desired course will cause deflection of the L.R. meter in one direction, while with the other setting, deviation .to the right will cause deiiection of the L.R. meter in the opposite direction. Since the craft must be appreciably oi course4 to deflect the meter either way (i, e. merely turning the airplane momentarily will not deflect the meter), the ambiguity can cause confusion.

, It is'the principal object of the instant invenv tion to provide an improved method Yof and means for resolving ythe Aabove-described ambiguities.

Another object is-to `p rovide an improved course indicator system wherein a unitary indication of deviation from course'nand Vo fsense ,of bearing 8 Claims. (Cl. Z50-11) 2 setting is provided on the face of a single instrument.

A further object isto provide a system of the described type aifording a unitary indication in which the flight rules are the same whether the selected course is toward or away from the range, and to which the pilot can react properly with a. minimum of mental effort.

A further object of the present invention is to provide a system of the described type which4 employs the usual crossed-pointer indicator meter of an instrument landing system. Since it is not necessary to use both the course indicator and the instrument landing system at the same time, the same meter may be used for both purposes.

The invention will be described with reference to the accompanying drawing, wherein:

Figure 1 is a schematic block diagram of a course indicator system embodying the present invention,

Figure 2 is an elevation of a portion ofv an airplane instrument panel, showing the indicators used in the practice of the invention, and

Figure 3 is a schematic diagram of a modification of the system of Figure 1, in combination with the indicator system of a radio instrument landing system.

For the purpose of illustration of the present invention, an omnidirectional range of the type described in the aforementioned Patent No. 2,253,958 is assumed. Refer to Figure l. The beacon itself is not shown. It is sufficient for the present explanation to state that the beacon radiates a'sin'gle carrier with variable phase modulation of one frequency a and a subcarrier modulation of frequency modulated in turn with a constant phase signal of frequency e.

The equipment to be carried on` an aircraft includes a radio receiver l capable of receivingthe doubly modulated range signal. A filter 3 separates the variable phase signal of frequency a from the receiver output, and a second filter 5 separates the subcarrier of frequency together with its constant phase sidebands of frequencies -I-a and -a.

The modulated subcarrier signal is demodulated by a demodulator 1, providing a constant phase output of frequency a. This is the reference phase voltage, and is applied through an adjustable phase shifter 9 to one pair of terminals of a wattmeter Il. The output of the lter 3, hereinafter referred to as the directional phase voltage is applied to the other pair of terminals of the wattmeter Il.

`The reference phase output of the phase shifter 9 is applied through a 90 phase shifter I3 to one pair of terminals of a second wattmeter I5. The other pair of terminals of the wattmeter I5 is connected to the lter 3. The adjustable phase shifter 9 is provided with a scale I1, calibrated in degrees, and a pointer I9 for indicating the bearing of the course 'selectedby adjustment di the phase -shifter 9.

The wattmeters II and I5 are arranged with their pointers crossing over a, common dial. The

springs or other bias means adjusted so thattheir -zero indications are central, with the pointers crossing each other atright angles.

In the operation of the system A'of Figure 1,'=the phase relationship between the directional phase output of the lter 3 and .the vreference .phase output of the demodulator I depends on the bearing of the receiver from the range transmitter. For example, if the aircraft is due east of the range transmitter (90 bearing), `the directional signal leads the reference signal by 90.

:'Now suppose it -is desired toiiy toward t-he .range station, Non .a course "bearirrg 45 degrees. The `phase '-shifteris :adjusted .to provide 'a phase lead 1in :the reference '.sign'al 'of :90 plus '45", er 135?. The'dial I1 is'arrangecl so .that 'with this adjustment, the pointer :t9 `.indicates v41.5. When thezairplane is on .the '1455. course lline, .the 4output demodulator 1, and .hence i90 .behind the .output of :the `zphase .shifter .9. .Thus .the two 'inputs to the Wattmeter .II are 90-cutter `phase with .each other, fand the meter read'slzero, .or Jon course.

If 'the airplane should get aofi course `to the right, i-i. -e. :to the .north 'of :the selected .45 course since it is Iying toward -the range, .the `output i 'the iilter would be #less fthan l145 ahead 'fof that :of the demodula'tor TLIand thus `more than 90 behind that of the phase shifter 9, .causingr the Wattmet'er fII t'o .defiecti'to'.theiright. 'Similarlyptheimeter II -will deflect to Lthe ileftif lth'e plane issouth .of :theselected i451course- .'Ihe zoutpu't lof .the .phaseishifter 9 is lshifted a further-90 by the 190 zphase shifter LI3. .'Although .this shift could ibes'in itherfdirec'tiomlet us assume that it is an advance in phase. "The output fof the iphase `slfiifter .|13 then llead-s that fof the demo'dulator 19 lby ja total 'of .135#l-l90, or 225. -When thefplaneiison-course, the outputfoi the ill-ter .-3 .leads that1o'f the :dem'odulat'or 7 :by 45"?, 'Sand 'isthus .180 behind that fof the phase shifter I9. Thisfcauses almaximumfupwardideflection 4of fthe .pointer lof' the 'Wattmeter 115, `linklicating that ftheFrangeris-.ahead `on '.the ;45 course.

As." ightr is fcontinued-al'ongithe .selected course, the meter I5 'will-'continue -lto fbe 'deflected-upward-lundi I.the range .station iis reached. When ifectional phase v.signal :reverses 1in .p'hase, "to lead the ireference .phase fou-tput fo'f 'the -demodulator 1 by'.225. This reversalin'phaseappears-at the outputs .ofthefphasershifterslwamd .-'I 3.

:The ftWo inputs to ftheivvattmeter Il-I :Wi-l1 -s'till be 90 out of phase with each other, and Ithe meter .IlI \Wi11=continueto.read zero, findicating that y".the :craft fis fstill on fan ie'xtension 'of lthe voriginal 45 .course Thertwofinputstothe wattm'eter 1I.5 will now ibe .in phase Jinstead 'of 180 out :of "phase, causing it '#to deiiect its Apointer downward rand indicate that the rangeds-behind, .a's'far as the l5coursesis-y concerned.

.The left-right findication's '-will 4l'still E"be correct for continuation of the flight y)away 'from ihe range, Ain 'ithe 'recipr'dcal :of :the fforiginally fselecttangente- 'fro meters II and I5 are provided with .restoring the Jangenthexntheriirection along the same course ilinie. the phase kshifter -9 is adj-usted to make the indicator I7, I9, read 225, the actual Fbearing of the desired course. It will be appar- ..ent without :further detailed explanation that :this would cause the meter I5 to deflect upward,v

indicating "range ahead, and will reverse the *sense -'of the 4`left-right indications to conform 'Withiiiglitiintheidesired direction.

Referring 'to Figure 2, the course bearing selector '.in'dicator ylil, .I19 and the crossed pointer indicator 2l are mounted adjacent each other on 'an airplane instrument panel 25, preferably near a compass indicator 2l. The bearing seleccenter *position *With this arrangement white 'is always Aassociated "with "flying toward the range, 'and black is railways associated with ilying away from the range. Thus, to `i'iy a "c'ours'e toward 'the "range, the whiteend ofthe pointer "I9 'isfse't *tothe bearling from th'erarige 'o'i' 'the desirdline o'f liigh't. Wh'en on'course, vthe jpoiliter of'themter 'I'I W'l be centeredfandthepointer of the meter I5 will be in the ulpr'('wliit) or range-'ahead sector.

.'Similaly, 'for radial li'light away from the range, the Tblak 4end .of .the Apointer .T9 isset 4to the T bear'ing' 'from Lthe range ofthe desiredline of iight. When .on course, .the .It-R. ...pointer .is centered.a.nd.the.pointer of .the .meter .I5 .isdnthe vblack sector. When :used .to determine .bearings for .a position ".'x, .theselector ITI `is.adjustedLto center .the .meter lll., 'the .sector clor indicated by .meter f1.5 -is noted, and `the bearing .is reajd against the similarly colored end of pointerw. 1t A.should -be .noted .that athe .range indicators showmerely .the l.angular l position `vwith respect to a .meridian `of the line .through .th'e @range .fstationandthecraft, and.dofnot give anyiindication of the actual .heading .of fthe .air-plane. This .Linformation is lplovided lby J.the compass 2a. For radial Hight through ithe ran-ge, l"the zairplaneiis always =-.turned :so 'that its compass-:heading 2indicated by the compass 21, agrees approximately with the:indicationftlreblackendlofithe l.slec.. .torlpointer :I9

Jntradial :.flight, scorre'cticn'ifor deviations trom the fdesired `course :is .made-fat all rtizn'es by turning :the :zaiisplane :slightly toward the ldr-:centered vertical xpiointer :of the crossed-pointer iindi Gatorszfl. 4

A v.syst-.em of Athe :aboveidescxibed l"type 'can be combinedconvenientiy1withb1ind-flandingfequipment, .affording double use soflthecrossedpomter indicator. Refer'rtoJFigui-e-3, whereinftheirange receiver :andithermeansffor: separating the reference .aand vdirectional 'phase -isignals #are #represented by a single blockl33. lnftlielmodication ofsiigure .3, phase ccmparisonfoircuits $5 and -91 are :substituted :for fthe 'wattmeters fII fan-d TF5. These'ircuitsimaybe miftherblancelmcdulatcr type, dike .ltiiat iin 'illigure 32 v:rif Cth'e Jabove- :menticric FU. .'S."lPtent No.=12,208377. Ifor jany other known devices providing' DAQ -.cutputs "dt f inagnitude and polarity depending upon the phase relationship between two A.C. inputs.

The aircraft equipment includes an instrument landing system comprisinga localizer receiver 39 and a glide path receiver 4i, designed in accord-.- ance with known practice to respond to. respec-l tive beacon transmitters (not shown). The 1ocalizer receiver 39 provides D.C. output of one polarity when the airplane is to the right of a predetermined'glide path, and output of the opposite polarity when the craft is to the left of the glide path. Similarly, the receiver 4| provides output of one polarity or the other when the plane is respectively above or below the glide path. Y

The indicator 2| in the system of Figure 3 is provided with two D.C. meter movements 43 and 45, with pointers normally centered vertically and horizontally respectively. The meter 43 is connected to a double-throw switch 41, through which it may be connected selectively to the phase comparison circuit 35 or to the localizer receiver `39. The meter 45 is connected to a similar switch 49, 4for connection to the phase comparison circuit 31 or the glide path receiver 4 l. The switches 49 and 41 are mechanically ganged to switch both meters together. Thus the crossed pointer indicator may be used either for blind landing, or for the above-described omnidirectional range indications. A cathode ray oscilloscope tube 22 may be used instead of the meters 43 and 45, with its horizontal and vertical deflection means 44 and 46 connected respectively to the phase comparison circuits 35 and 31. With this arrangement, the indication is in the form of a luminous spot, at a position on the cathode ray screen corresponding generally to the position of the intersection of the pointers of the meters 43 and 45 on the dial It has been assumed that the output of the glide path receiver is zero when the airplane is on the glide path. Some glide path systems, such as those based on following a line of constant signal strength, provide a predetermined constant output when the craft is on the proper path, and more output or less output when the craft deviates above or below said path. It will be apparent to those skilled in the art that such systems can be adapted to the system of Figure 3 by providing an auxiliary source of bias, for example, withl the glide path receiver 4I, to cause central indication by the meter 45 when the craft is on the correct glide path.

I claim as my invention:

1. In a course indicator for omnidirectional radio ranges, including means providing a reference phase signal and a directional phase signal, and course bearing selector means for shifting the phase of one of said signals in accordance with the bearing of a predetermined course, visual indicator means for said bearing selector comprising a scale and pointer providing both direct.

and reciprocal bearing indications and having two differently marked portions for providing visual distinguishability between said direct and reciprocal indications, a unitary indicator device including two orthogonally related pointers and respective deflection means, means responsive to the phase relationship between said phase shifted signal and the other of said inst-mentioned signals to actuate one of said deection means to deflect one of said orthogonal pointers to show deviation from said course. means responsive to the phase relationship between said two lastmentioned signals toactuate the other of said de flection means to deect thel other of said two orthogonal pointers to show the sense of said course, saidindicator means including, in cooperative relationship with said last-mentioned pointer, a scale having two portions diierently marked like respective vdifferently marked por. tions of `said bearingindicator means.

2. In a, course indicator system for omnidirectional radio ranges, including means providing a reference phase signal and a directional phase signal, and course bearing selector means for shifting the phase of one of said signals in accordance with the bearing of a predetermined course, visual indicator means for said bearing selector comprising a scale and pointer providing both direct and reciprocal bearing indications and having `two differently marked portions for providing visual distinguishability between said direct and reciprocal indications, indicator means responsive to the phase relationship between said phase shifted signal and the other of said firstmentioned signals to show deviation from said course, and further indicator means responsive to the phase relationship between said two lastmentioned signals to show the sense of said course, said last-mentioned indicator means including two portions diierently marked like respective differently marked portions of said bear ing indicator means.

3. In a course indicator system for omnidirectional radio ranges, including means providing a reference phase signal and a directional phase signal, and course bearing selector means for shiftingthe phase of one of said signals in accordance with the bearing of a predetermined course, visual indicator means for said bearing selector comprising a scale and pointer providing both direct and reciprocal bearingindications and having two diierently marked portions for providing visual distinguishability between said direct and reciprocal indications, indicator means responsive to the phase relationship between said phase shifted signal and the other of said firstmentioned signals to show deviation from said course, and further indicator means responsive to the phase relationship between said two lastmentioned signals to show the sense of said course, said last-mentioned indicator means including two portions diierently marked like respective differently marked portions of said bearing indicator means.

4. In a combined course indicator for omnidirectional radio ranges and glide path indicator for instrument landing, systems, means providing alreference phase signal and a directional phase signal, and a course bearing selector for shifting the phase of one of said signals in accordance with the bearing of a predetermined course, means responsive to the phase relationship between said phase shifted signal and to the other of said first-mentioned signals to provide a voltage varying in accordance with deviation from said course, means responsive to the phase relationship between said last-mentioned two signals to provide a second voltage of polarity depending upon the sense of saidv course, glide path receiver means providing two further voltages varying in accordance with deviation horizontally and vertically respectively from a predetermined glide path, a unitary indicator device including two orthogonally related deection means, and means for selectively applying said rst pair of said voltages or said second pair of voltages respectively to said deflection means.

In a "course indicatorisystemffionmnidirec@ tional radio ranges;` including imeansf=providingfa reference phase signal :.and a'directonal :phase signal, and 'course bearing l"-selector means for shifting the phasefof` one of -saidssignalszinea cordance with the bearing-of n=fpredetermined course, visual indicatormeansfer'saxi bearing selector comprising -a--scaieyandipointer providing both direct and reciprocal vuinrinjg' j"indicaticmrs and having two differentlycmarkcdipltionsior providing visual Vd-isting-uisheaiiitybetweensaid direct and reciprocaiirnzicaticns,farunitary-@indic cator devi-ce lincluding orthogonaliy related deflection means, means -re$ponsiveto thephase relationship between said Jfhase shiftedisignal and the other 'of said f1-rst'.-rnentforret1-sig=r1ais--to actuat'e oneeof isaid -deiiection-meansf`to ,show deviation from said course-meansfresponsive'fto the phase yrelationship"vbetween#said twoylastmentioned signalsv Ito actuatethe v1 other of flsaid deflection 'means to show: thesense 'of 'said course, said kindicator 4meansiirc'luding, "jin cooperative relationship with 'said last-rnention'e'd 'fd-erlection means, two Yportions 'd'iiferentjjly I narxkeri like respective vdifferently lmanned r.portions jof i said bearing indicator means. v

'6; In a 'course indicatonsystemfor,oninidirectional .radio ranges, includingmeans providing reference phase signal andai'recti'onal phase signal, and a course bearing.sl'ectorfor shifting the phase of one ofjsaid signalsgjnaccordance with' the bearing offajpredetemiined oursea unitary indicator Y'device mcindingjtwo orthg -onally related deflection means, meansresponsve means to .show deviation from saidY course, and

means responsive to thephase relationship hetween said last-mentioned two signals to actuate the other of said deflection meanstoshowdire tiono travel along said course.

,17. :A system for indicating thefphase relationship-between two alternating `voltages comprising a unitary indicator device having two pointers crossing eachother kand normally. centered ver.- tically and horizontally respectively, means responsive to diierence in phase between said two voltages to deiiect one of said pointers,'.means `for shifting the .phase of -one ofy said voltages ,by'90", and means. responsive to difference in phase between said phase shifted vvoltagegand the other of'said mst-mentioned voltages to deflect the other of said pointers.

. 8.L A system for indicating the phase lrelationship between tivo alternating voltages. comprising afunitary indicator device having a -single vface and two .orthogonally `related 4deflection means, means responsive to difference in phase between said two voltages toA ac tuate voneof said deflection means, means-for shifting the-phase of one of said --voltages 90, and means responsive to difierence in phase between saidphase shifted voltage 'and the other ofl said rfirstment ionen voltages to 'actuate the other of said, deflection y means.

yDAVID (G. yC. I iUQIl. 

